Polymer blends with mould-release agents

ABSTRACT

A thermoplastic polymer mixture comprising at least on thermoplastic polycarbonate polymer, and at least one mold release agent including at least one polyol component, is described. At least one polyol component (I) of the mold release agent consists of a parent substance with at least 4 carbon atoms, at least 3 hydroxyl groups, at least one hydroxyl group esterified with an aliphatic carboxylic acid, and at least one free hydroxyl group.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

The present patent application claims the right of priority under 35U.S.C. 119 and 35 U.S.C. 365 of International Application No.PCT/EP99/09693, filed 9 Dec. 1999, which was published in German asInternational Patent Publication No. WO 00/37550 on 29 Jun. 2000, whichis entitled to the right of priority of German Patent Application No.198 59 050.4, filed 21 Dec. 1998.

FIELD OF THE INVENTION

The present invention provides thermoplastic polymer mixtures containingat least one mould release agent with a polyol component consisting of aparent substance with 4 or more carbon atoms, 3 or more hydroxyl groups,more than one hydroxyl group esterified with aliphatic C₁-C₃₂ carboxylicacids and one or more than one free hydroxyl group, the use of suchpolyol components as mould release agents for thermoplastic polymermixtures and moulded items made from these thermoplastic polymermixtures.

BACKGROUND OF THE INVENTION

When processing thermoplastic polymer mixtures, the production ofmoulded parts some of which have extremely complicated spatial shapes isa main application. Mould release agents are added to the polymermixture itself or placed in the machines during processing in order toensure, or simplify still further, removal of the moulded parts from themould. In addition, these are intended to improve the surface quality.

The disadvantage of this procedure is contamination of the product withadditives which can have a detrimental effect on the moulded item duringpreparation, storage or use.

Esters of long chain fatty acids with hydroxy components, in particularglycerine, have proven useful in the prior art.

DE-OS-20 64 095 describes the addition to polycarbonates of fatty acidesters of trihydric alcohols as mould release agents.

DE-OS-25 07 748 describes the improvement in the mould releasecharacteristics of polycarbonates due to the addition of polyalcoholscompletely esterified with fatty acids.

DE-OS 27 01 725 describes the addition of part-esters of specificalcohols to polycarbonates for the purpose of mould release.

JP-A-45-24 439 describes the addition to polycarbonates of part-estersin amounts of 0.05 to 5% for the purpose of mould release.

JP-A-72-45 934 describes antistatic-modified polycarbonates with 0.1 to5 wt. % of fatty acid monoglycerides.

JP-A-60-81 245 describes the addition of part-esters to low-chlorinepolycarbonates in order to prevent corrosion of the moulds.

JP-A-2-225 558 describes polycarbonate sheets which contain part-estersof polyols and aliphatic monocarboxylic acids.

Japanese patent application 90-12-510 describes substrates for CDs whichconsist of polycarbonate and contain 0.002 to 5% of fatty acidmonoglycerides.

Japanese patent application 90-294 979 describes polycarbonates foroptical discs which contain 0.06 to 0.09% of glycerine monostearate.

U.S. Pat. No. 4,131,575 describes the addition to polycarbonates of fullesters of polyhydric alcohols or monoesters of polyhydric alcohols, toimprove mould release.

U.S. Pat. No. 4,743,641 describes the addition of glycerinemonostearate, diglyceride monostearate, glycerine monopalmitate orsorbitane monostearate to polycarbonates.

EP-A-205 192 describes polycarbonate mixtures to which has been addedesters of glycerine and of pentaerythritol. Glycerine monostearate ispreferred in that document.

EP-A-213 413 describes the addition of part-esters to polycarbonates foroptical purposes.

EP-A-417 775 describes moulded items for optics made of polycarbonateswhich contain fatty acid monoglycerides.

EP-A-511 640 also describes the addition of part-esters topolycarbonates for optical purposes.

EP-A-732 360 describes polycarbonate mixtures with mixtures of glycerinemonostearate and glycerine tristearate.

The mould release agents in the prior art, such as for example thefrequently used glycerine monostearate, have the disadvantage that theycan lead to reactions with the polycarbonate. This impairs the thermaland oxidative resistance of the materials which may be expressed, forexample, by yellowing. This is undesirable, in particular for opticalapplications of polycarbonate. This applies in particular to processingprocesses which involve high thermal stress for the material or forapplications which require special optical quality. The mechanicalproperties of the polymer may also be modified undesirably as a resultof these reactions. In addition coatings may appear on parts of themachines.

In the case of fully esterified alcohol components, the mould releasecharacteristics are inadequate.

There is therefore a constant demand for novel mould release agents forthermoplastic polymers such as, for example, polycarbonate and/orpolycarbonate blends.

SUMMARY OF THE INVENTION

The object therefore consists of developing a mould release agent forpolycarbonates which has a very low, or even zero, tendency to reactunder the conditions of preparation and processing, especially duringthe preparation of products for optical applications such as compactdiscs and digital versatile discs (DVDs), have a good mould releaseeffect and thus lead to improved quality and higher data security in thecase of optical applications. This is achieved by polymer mixturesaccording to the invention.

Accordingly, the present application provides thermoplastic polymermixtures containing at least one polycarbonate and at least one mouldrelease agent with at least one polyol component wherein at least onepolyol component (I) consists of a parent substance with 4 or morecarbon atoms, 3 or more, preferably 4 or more, hydroxyl groups, morethan one hydroxyl group esterified with aliphatic carboxylic acids andone or preferably more than one free hydroxyl group.

DETAILED DESCRIPTION OF THE INVENTION

Thermoplastic aromatic polycarbonates in the context of the presentinvention are either homopolycarbonates or copolycarbonates; thepolycarbonates may be linear or branched in a known manner.

These polycarbonates are prepared in a known manner from diphenols,carbonic acid derivatives, optional chain stoppers and optionalbranching agents.

Details of the preparation of polycarbonates have been presented in manypatent documents over the last 40 years. By way of example, reference ismade here only to Schnell, “Chemistry and Physics of Polycarbonates”,Polymer Reviews, volume 9, Interscience Publishers, New York, London,Sydney, 1964, to D. Freitag, U. Grigo, P. R. Müller, H. Nouvertne',BAYER AG, “Polycarbonates” in Encyclopedia of Polymer Science andEngineering, volume 11, 2nd edition, 1988, pages 648-718 and finally toDrs. U. Grigo, K. Kirchner and P. R Müller “Polycarbonate” inBecker/Braun, Kunststoff-Handbuch, vol. 3/1, Polycarbonate, Polyacetale,Polyester, Celluloseester, Carl Hanser Verlag, Munich, Vienna 1992,pages 117-299.

Suitable diphenols for preparing polycarbonates are, for example,hydroquinone, resorcinol, dihydroxydiphenyls,bis-(hydroxyphenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes,bis-(hydroxyphenyl)-sulfides, bis-(hydroxyphenyl)-ethers,bis-(hydroxyphenyl)-ketones, bis-(hydroxyphenyl)-sulfones,bis-(hydroxyphenyl)-sulfoxides,α,α′-bis-(hydroxyphenyl)-diisopropylbenzenes, and their ring-alkylatedand ring-halogenated compounds.

Preferred diphenols are 4,4′-dihydroxydiphenyl,2,2-bis-(4-hydroxyphenyl)-propane,2,4-bis-(4-hydroxyphenyl)-2-methylbutane,1,1-bis-(4-hydroxyphenyl)-p-diisopropyl-benzene,2,2-bis-(3-methyl-4-hydroxyphenyl)-propane,2,2-bis-(3-chloro-4-hydroxy-phenyl)-propane,bis-(3,5-dimethyl-4-hydroxyphenyl)-methane,2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,bis-(3,5-dimethyl-4-hydroxyphenyl)-sulfone,2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane,1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene,2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane,2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane,1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethyl-cyclohexane and4,4′-(m-phenylenediisopropylidene)-diphenol.

Particularly preferred diphenols are 2,2-bis-(4-hydroxyphenyl)-propane(BPA), 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane,2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane,4,4′-(m-phenylene-diisopropylidene)-bisphenol (CAS No: 13595-25-0)(BPM), 1,1-bis-(4-hydroxyphenyl)-cyclohexane and1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (TMC).

These and other suitable diphenols are described, for example, in U.S.Pat. Nos. 3,028,635, 2,999,835, 3,148,172, 2,991,273, 3,271,367,4,982,014 and 2,999,846, in German patent documents 1 570 703, 2 063050, 2 036 052, 2 211 956 and 3 832 396, in French patent document 1 561518, in the monograph “H. Schnell, Chemistry and Physics ofPolycarbonates, Interscience Publishers, New York 1964” and in Japanesepatent documents 62039/1986, 62040/1986 and 105550/1986.

In the case of homopolycarbonates, only one diphenol is used; in thecase of copolycarbonates, several diphenols are used.

Polymer mixtures which contain at least one polycarbonate with diolblocks made from bisphenol A and/or trimethylcyclohexyl bisphenol (TMC)are preferably used, preferably those chosen from the group ofhomopolymers of bisphenol A, copolymers of bisphenol A with TMC or ofcopolymers with 5 to 50 wt. % of TMC.

Suitable carbonic acid derivatives are, for example, phosgene ordiphenyl carbonate.

Suitable chain stoppers are either monophenols or monocarboxylic acids.Suitable monophenols are phenol itself, alkylphenols such as cresols,p-tert.-butylphenol, p-n-octylphenol, p-iso-octylphenol p-n-nonylphenoland p-iso-nonylphenol, halogenophenols such as p-chlorophenol,2,4-dichlorophenol, p-bromophenol, amylphenol and 2,4,6-tribromophenoland mixtures of these.

Preferred chain stoppers are phenol and/or p-tert.-butylphenol and/orp-cumylphenol.

Suitable monocarboxylic acids are benzoic acid, alkylbenzoic acids andhalogenobenzoic acids.

Preferred chain stoppers are phenols of the formula (I)

in which R is hydrogen, tert.-butyl or a branched or unbranched C₈and/or C₉ alkyl group. However, p-cumylphenol may also preferably beused.

The amount of chain stopper to be used, preferably in a phase interfaceprocess, is 0.1 mol. % to 5 mol. %, with respect to the particulardiphenols used. The addition of chain stoppers may take place before,during or after phosgenation.

Suitable branching agents are the trifunctional or more thantrifunctional compounds known from polycarbonate chemistry, inparticular those with three or more than three phenolic OH groups.

Suitable branching agents are, for example, phloroglucine,4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hept-2-ene,4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane,1,3,5-tri-(4-hydroxyphenyl)-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane,tri-(4-hydroxyphenyl)-phenylmethane,2,2-bis-[4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-propane,2,4-bis-(4-hydroxyphenyl-isopropyl)-phenol,2,6-bis-(2-hydroxy-5′-methyl-benzyl)-4-methyl-phenol,2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane,hexa-(4-(4-hydroxyphenyl-isopropyl)-phenyl orthoterephthalate,tetra-(4-hydroxyphenyl)-methane,tetra-(4-(4-hydroxyphenyl-isopropyl)-phenoxy)-methane and1,4-bis-(4′,4″-dihydroxytriphenyl)-methyl)-benzene and also2,4-dihydroxybenzoic acid, trimesic acid, cyanuric chloride and for afew applications even preferably3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-hydroindole.

The amount of optionally used branching agent is 0.05 mol. % to 2 mol.%, again with respect to the particular diphenols used.

The branching agent may either be initially introduced to the phaseinterface process in the aqueous alkaline phase with the diphenols andthe chain stoppers or may be added dissolved in an organic solvent. Inthe case of a transesterification process, the branching agent is usedtogether with the diphenols.

All these steps for preparing thermoplastic polycarbonates are familiarto a person skilled in the art.

Polyol components which can be used according to the invention are thosewith 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms, particularlypreferably 5, 6 or 7 carbon atoms, very particularly preferably 5 or 6carbon atoms and even more preferably 5 carbon atoms.

Polyol components (I) with the following general formulae are preferred:

in which the substituents X, independently, are hydrogen atoms oraliphatic acyl groups, with the proviso that more than one X is an acylgroup and more than one X is a hydrogen atom, and R is a hydrogen atomor a linear or branched C₁ to C₁₀ alkyl group, preferably methyl, ethylor propyl.

The groups Y, independently, are hydrogen atoms, alkyl or aryl groups,wherein hydrogen atoms, methyl, ethyl, propyl, butyl and phenyl groupsare preferred. Hydrogen atoms and methyl groups are particularlypreferred. It is very particularly preferred that a carbon atom with ahydrogen substituent is not located immediately adjacent to a carbonatom with hydroxyl groups.

Preferred acyl groups X are fatty acid ester groups with 2 to 30 carbonatoms, particularly preferably C₅-C₂₅ fatty acids, very particularlypreferably C₈-C₂₄ fatty acids and even more preferably C₁₂-C₂₂ fattyacid and mixtures of these. A person skilled in the art finds the bestexamples among C₁₆-C₂₀ fatty acids, more preferably C₁₆-C₁₈ fatty acidsand mixtures of these.

Examples of such acyl groups are groups from acetic acid, propionic acidand butyric acid and also groups from myristic acid, palmitic acid orstearic acid, arachidic acid and behenic acid and mixtures of these,preferably mixtures of stearic acid and palmitic acid.

Polyol components in which the number of esterified and free hydroxylgroups is the same are preferred.

Preferred polyol components are diester derivatives of pentaerythritol,in particular diesters of pentaerythritol with stearic acid.

Polyol component (I) may be used in amounts of 0.005 wt. % to 0.5 wt. %,preferably 0.01 wt. % to 0.2 wt. %, very particularly preferably 0.015wt. % to 0.1 wt. % and even more preferably 0.02 wt. % to 0.08 wt. %.

The polyol component may be used either as an individual substance or asa mixture of two or more polyol components and/or other components. Theratio of the amount of polyol component (I) in the mould release agentto other optionally present components in the mould release agent ispreferably greater than 1:1.

A person skilled in the art obtains good results when the proportion ofpolyol components with less than one free hydroxyl group or polyolcomponents with less than two esterified hydroxyl groups in the entiremould release agent are each less than 24 wt. %, preferably less than 20wt. %, particularly preferably less than 15 wt. % and even morepreferably less than 10 wt. %.

Conventional additives may be added, in known amounts, to thethermoplastic polycarbonates to be removed from moulds in accordancewith the invention, for example stabilisers against the effects of heat,moisture and UV radiation, such as phosphorus compounds (such asphosphoric acid, phosphates, phosphites, phosphonites, etc.), optionallycombined with monomeric or polymeric epoxides, N-containing heterocycliccompounds such as triazoles or benztriazoles, also flame retardants suchas aliphatic or aromatic or perfluorinated aliphatic alkali metal oralkaline earth metal sulfonates, colorants, fillers, foaming agents, andantistatic agents. In the case of optical applications, those componentswhich do not impair the transparency of the material are preferred.

Addition of the polyol component to the thermoplastic polycarbonates maytake place, for example, by adding the polyol component during workingup of the polymer solution of the thermoplastic polycarbonates or of themelt of the thermoplastic polycarbonates; addition preferably takesplace when compounding the final, thermoplastic polycarbonates.

Conventional additives which are known for use with polycarbonates maybe admixed in a known manner either before addition of the polyolcomponent, when adding the polyol component or after addition of thepolyol component to the polycarbonates.

The invention also provides use of polyol components (I) as mouldrelease agents for thermoplastic polymer mixtures containing at leastone polycarbonate.

The invention also provides moulded items made from the thermoplasticpolymer mixtures mentioned above, preferably for optical applications,particularly preferably for optical data carriers, very particularlypreferably for compact discs and DVDs.

Polycarbonates which are easy to remove from moulds, in accordance withthe invention, may be further processed in the ways known forpolycarbonates for optical applications, particularly preferably foroptical data carriers, very particularly preferably compact discs andDVDs.

This processing may take place as a separate step using finally preparedpolycarbonates which are easy to remove from moulds and which areobtained for example as granules. Processing may also take place,however, after incorporation of the polyol component and/or conventionaladditives.

EXAMPLES

The following mixture was prepared:

Example 1

99.96 wt. % polycarbonate granules of bisphenol-A-PC withtert.butylphenol terminal groups and an average solution viscosity of1.20 (measured in methylene chloride at 25° C. and a concentration of0.5 g in 100 ml of methylene chloride)

0.04 wt. % Loxiol EP 728 (fatty ester diester of pentaerythritol),Henkel KGaA

and intensively mixed in a sealed container. Then the mixture wascompounded on a twin-screw compounder of the Werner Pfleiderer ZSK 53type at a bulk temperature of about 240° C.

Comparison Example 1

(without a Mould Release Agent)

Polycarbonate granules of bisphenol-A-PC with tert.butylphenol terminalgroups and an average solution viscosity of 1.20 (measured in methylenechloride at 25° C. and a concentration of 0.5 g in 100 ml of methylenechloride) were compounded on a twin-screw compounder of the WernerPfleiderer ZSK 53 type at a bulk temperature of about 240° C.

Comparison Example 2

(with Glycerine Monostearate)

The following mixture was prepared:

99.96 wt. % polycarbonate granules of bisphenol-A-PC withtert.butylphenol terminal groups and an average solution viscosity of1.20 (measured in methylene chloride at 25° C. and a concentration of0.5 g in 100 ml of methylene chloride)

0.04 wt. % Loxiol EP 129 (glycerine monostearate), Henkel KGaA

and intensively mixed in a sealed container. Then the mixture wascompounded on a twin-screw compounder of the Werner Pfleiderer ZSK 53type at a bulk temperature of about 240° C.

Comparison Example 3

(with Pentaerythrityl Stearate)

The following mixture was prepared:

Example 1

99.96 wt. % polycarbonate granules of bisphenol-A-PC withtert.butylphenol terminal groups and an average solution viscosity of1.20 (measured in methylene chloride at 25° C. and a concentration of0.5 g in 100 ml of methylene chloride)

0.04 wt. % Loxiol P 861/3.5 (tetraester of pentaerythritol), Henkel KGaA

and intensively mixed in a sealed container. Then the mixture wascompounded on a twin-screw compounder of the Werner Pfleiderer ZSK 53type at a bulk temperature of about 240° C.

Measuring the Static Friction

Static friction is the frictional index which is derived from the forcerequired to set in motion bodies which are stationary with respect toeach other (plunger/test item).

The coefficient of static friction is defined as follows:

F _(R) =μ*F _(N)  (equ. 1)

after rearranging: μ=F _(R) /F _(N)  (equ. 2)

F_(N)=normal force, F_(R)=frictional force, μ=coefficient of friction

In the case of circular motion, the following relationship applies:F_(R)=M_(d)/r_(m) (equ. 3) M_(d)=torque, r_(m)=average radius of area offriction (ring area)

M _(d) /r _(m) =μ*F _(N)  (equ. 4)

after rearranging: μ=M _(d)/(r _(m) *F _(N))  (equ. 5)

In a special coefficient of friction mould, a disc-shaped test item withan outer diameter of 92 mm and a thickness of 2.6 mm is prepared. Thishas a 5 mm high and 3 mm wide ridge at the outer edge, on which arelocated flat indentations, comparable to a toothed belt disc, wherebythe torque is transferred from the mould to the test item.

This enables direct determination of the coefficient of static friction(equ. 5) of a disc-shaped test item, immediately after it hassolidified. The relationship that the frictional force is proportionalto the torque (equ. 3) is used here. On opening the mould, a plungerconnected to a torque sensor and with a defined normal force F_(N)against the moulded part (friction partner) is introduced. On the otherface of the moulded part, the test item is held in place and set inrotation. The coefficient of static friction between the plunger and thetest item is determined from the torque measured at the plunger. Sincethe friction is caused by the unevenness of the surfaces slipping pasteach other (hooking into each other), the plunger was designed with anaverage surface roughness Ra=0.05 μm.

The materials (material 1 and comparison material 1, comparison material2 and comparison material 3) were melted in an injection mouldingmachine and injected into the sealed coefficient of friction mould witha wall temperature of 100° C. at a melt temperature of 300° C. andretained for a period of 15 sec at a follow-up pressure of 550 bar.

After a residual cooling time of 20 sec, the mould was opened veryslightly and the coefficient of friction was determined.

The following values were obtained:

Material Coefficient of static friction μ₀ Material 1 0.82 Comparisonmaterial 1 1.07 Comparison material 2 0.72 Comparison material 3 1.04

It can be seen that with a small concentration of mould release agentonly the product according to the invention and the comparison productwith glycerine monostearate as mould release agent clearly lower thestatic friction.

Measuring Product Stability when Producing CDs

To measure the product stability, CD crude mouldings were prepared on aCD injection moulding machine of the Netsal Discjet 600 type usingmaterial 1 and comparison material 2 described above, these having athickness of 1.2 mm and an outer diameter of 120 mm. In order to avoidscattering and diffraction of light in the colorometric measurements, apolished cavity plate without a pit structure was used. Processing ofthe materials took place with different machine settings:

Setting 1: Cylinder temperatures (feed end/compression/cylinderhead/nozzle) 315/320/320/320° C. maximum rate of injection 130 mm/secmould (initial temperature) 55° C.; cycle time 4.6 sec.

Setting 2: Cylinder temperatures (feed end/compression/cylinderhead/nozzle) 315/340/350/350° C. maximum rate of injection 110 mm/secmould (initial temperature) 55° C.; cycle time 4.9 sec.

Setting 3: Cylinder temperatures (feed end/compression/cylinderhead/nozzle) 315/360/380/380° C. maximum rate of injection 100 mm/secmould (initial temperature) 55° C.; cycle time 5.5 sec.

Setting 4: Corresponding to setting 2, wherein however the cycle isinterrupted by a 5 minute machine stoppage. Each fifth disc afterre-starting the injection moulding machine was used for the followingmeasurements.

The melt viscosity, the yellowness index, the concentration of phenolicOH groups and the concentration of free tert.-butylphenol of the CDcrude mouldings were measured. The following values were obtained:

TABLE 1 Melt viscosity in Pa*s (300° C./1000 s⁻¹) Setting 1 Setting 2Setting 3 Setting 4 Sample (320° C.) (350° C.) (380° C.) (350° C. +stop) Material 1 66 66 65 65 Comparison 63 63 63 61 material 2

TABLE 2 Yellowness index YI according to ASTM E 313 Setting 1 Setting 2Setting 3 Setting 4 Sample (320° C.) (350° C.) (380° C.) (350° C. +stop) Material 1 1.02 1.02 1.02 1.38 Comparison 1.10 1.16 1.18 1.48material 2

TABLE 3 Phenolic OH in ppm Setting 1 Setting 2 Setting 3 Setting 4Sample (320° C.) (350° C.) (380° C.) (350° C. + stop) Material 1 110 115125 130 Comparison 120 130 135 145 material 2

TABLE 4 Free p-tert.-butylphenol in ppm Setting 1 Setting 2 Setting 3Setting 4 Sample (320° C.) (350° C.) (380° C.) (350° C. + stop) Material1 6 6 8 11 Comparison 9 11 19 20 material 2

Description of the methods of measurement in detail:

a) Melt viscosity measurement in high-pressure capillary viscometer

 The CD crude mouldings are cut into 6 to 8 mm strips and dried for 16 hat 110° C. under vacuum. Then the strips are inserted into a testchannel heated to 300° C. (diameter 10 mm), melted and pushed with aplunger through a nozzle with a diameter of 1 mm and a length of 20 mmwith a rate of shear of 1000 s⁻¹.

b) Yellowness index YI according to ASTM E 313

 The measurement was made perpendicular to the surface of the CD at aradius of 40 mm.

c) Phenolic OH

 The polycarbonate is dissolved in dichloromethane and titanium (IV)chloride is added, whereupon an orange-red complex is formed. Theextinction of this complex is determined photometrically at 546 nm.Calibration is performed with bisphenol A as an external standard. Thelimit of determination is about 20 ppm OH.

d) Free p-tert.-butylphenol

 10 g of polycarbonate are dissolved in methylene chloride andprecipitated with acetone and methanol. The precipitated polymer isfiltered off and the residual solution is concentrated down to about 20ml. Then the solution is analysed using high-pressure liquidchromatography.

 Chromatographic conditions: Reverse phase: C18; mobile solvent:water/acetonitrile (50%); flow: 1 ml/min; wavelength: 220 nm.

The test results demonstrate advantages for the material according tothe invention in all the properties measured.

What is claimed is:
 1. Thermoplastic polymer mixtures comprising: (a) atleast one polycarbonate selected from the group consisting of copolymersof bisphenol A with trimethylcyclohexyl bisphenol containing 5 to 50 wt.% of trimethylcyclohexyl bisphenol; and (b) at least one mould releaseagent with at least one polyol component; wherein said polyol component(I) of said mould release agent is selected from at least one member ofthe group consisting of polyols represented by the following formulas,

X independently represents a hydrogen or an aliphatic acyl residue of analiphatic carboxylic acid, and Y independently represents a memberselected from the group consisting of hydrogen, alkyl and aryl groups,said polyol component (I) having esterified groups and free hydroxylgroups, the number of esterified groups and free hydroxyl groups of saidpolyol component (I) being the same.
 2. The thermoplastic polymermixtures of claim 1 wherein the aliphatic carboxylic acids are selectedfrom C₂-C₃₀ fatty acids and mixtures thereof.
 3. The thermoplasticpolymer mixtures of claim 1 wherein the polyol component (I) is presentin amounts of 0.005 wt. % to 0.5 wt. %.
 4. The thermoplastic polymermixtures of claim 1 wherein in polyol component (I), a carbon atom witha hydrogen substituent is not located immediately adjacent to a carbonatom with a hydroxyl group.
 5. The thermoplastic polymer mixtures ofclaim 1 wherein the ratio of the amount of polyol component (I) in themould release agent to other optionally present components in the mouldrelease agent is greater than 1:1.
 6. The thermoplastic polymer mixturesof claim 1 further comprising at least one additive selected from thegroup consisting of stabilisers, flame retardants, antistatic agents,fillers, foaming agents and colorants.
 7. Moulded articles made from thethermoplastic polymer mixtures of claim
 1. 8. The thermoplastic mixturesof claim 2 wherein the aliphatic carboxylic acids are selected from thegroup consisting of C₅-C₂₅ fatty acids and mixtures thereof.
 9. Thethermoplastic mixtures of claim 2 wherein the aliphatic carboxylic acidsare selected from the group consisting of C₈-C₂₄ fatty acids andmixtures thereof.
 10. The thermoplastic mixtures of claim 2 wherein thealiphatic carboxylic acids are selected from the group consisting ofC₁₂-C₂₂ fatty acids and mixtures thereof.
 11. The thermoplastic mixturesof claim 2 wherein the aliphatic carboxylic acids are selected from thegroup consisting of C₁₆-C₂₀ fatty acids and mixtures thereof.
 12. Thethermoplastic mixtures of claim 2 wherein the aliphatic carboxylic acidsare selected from the group consisting of C₁₆-C₁₈ fatty acids andmixtures thereof.
 13. The thermoplastic mixtures of claim 3 wherein thepolyol component (I) is present in amounts of 0.01 wt. % to 0.2 wt. %.14. The thermoplastic mixtures of claim 3 wherein the polyol component(I) is present in amounts of 0.015 wt. % to 0.1 wt. %.
 15. Thethermoplastic mixtures of claim 3 wherein the polyol component (I) ispresent in amounts of 0.02 wt. % to 0.08 wt. %.
 16. The moulded articlesof claim 7 wherein said moulded articles are selected from the groupconsisting of compact discs and DVDs.
 17. The thermoplastic polymermixture of claim 1 wherein Y is selected independently from the groupconsisting of hydrogen, methyl, ethyl, propyl, butyl and phenyl groups.